As an Amora he was inferior to Rab in the knowledge of the laws of the ritual, but far surpassed him in his acquaintance with the Jewish civil law. Samuel developed and enriched the Jewish law in all its branches, and all his decisions have obtained Halachic force. None of his decrees, however, were possessed of such important results as the one by which he declared the law of the land to be just as binding on the Jews as their own law (dina d'malchuta dina). The object of this precept was not to bring about a compulsory toleration of the foreign legislation, but to obtain its complete recognition as a binding law, to transgress which would also be punishable from the religious point of view. This was an innovation which, after all, could only be approved by reason of the relations existing between the Babylonian Jews and the Persian states. Samuel's principle of the sanctity of the law of the land was a manifest contradiction of older Halachas, which treated foreign laws as arbitrary, and did not consider their transgression to be punishable. But the Amoraim had already succeeded in reconciling so many conflicting laws that these old and repellent decisions, and this new and submissive principle, were able to exist side by side. In the sequel Samuel's recognition of the laws of the country was a means of preservation to the dispersed nation. On the one hand it reconciled the Jews to living in that country into which they had been cast by remorseless fate. Their religious consciousness did not feel at variance with the laws set up for their observance, which were seldom humane. On the other hand, the enemies of the Jews, who in all centuries took as their pretext the apparently hostile spirit of Judaism, and advised the persecution and complete extermination of the Jewish nation, could be referred to a Jewish law, which, with three words, invalidated their contention. The Prophet Jeremiah had given to the families which were exiled to Babylon, the following urgent exhortation as to their conduct in a foreign land: "Seek the peace of the city whither ye have been carried away captives." Samuel had transformed this exhortation into a religious precept: "The law of the state is binding law." To Jeremiah and Mar-Samuel Judaism owes the possibility of existence in a foreign country.

Samuel possessed altogether a particular affection for Persian customs, and was consequently in exceedingly good repute at the Persian court, and lived on confidential terms with Shabur I. His contemporaries called him therefore, although it is not known whether as a mark of honor or of censure, "The king Shabur," and also "Arioch," the Arian (partizan of the neo-Persians). His attachment to the Persian dynasty was so great that it supplanted the affection for his fellow-countrymen in his heart. When Shabur extended his conquests to Asia Minor, 12,000 Jews lost their lives on the occasion of the assault of Mazaca-Cæsarea, the Cappadocian capital. Samuel refused to go into mourning for the victims, giving as his reason that they had fought against Shabur. He thus formed a peculiar type; living in the midst of the full tide of Judaism, immersed in its doctrines and traditions, he raised himself beyond the narrow sphere of his nationality, and was ever ready to extend his sympathies to other peoples and to take note of their intellectual efforts. Rab, entirely taken up with the affairs of his own nation, refused to allow the customs of the Persians to exert any influence on those of the Jews, and even forbade these latter to adopt any practice, however innocent, from the Magi: "He who learns a single thing of the Magi merits death." Samuel, on the other hand, learnt many things of the Persian sages. With his friend Ablaat, he used to study astronomy, that noble science which brings mortal man into closer proximity with the Deity. The low-lying plain between the Euphrates and the Tigris, whose wide-extended horizon is unbounded by any hill, was the cradle of astronomy, which, however, soon degenerated in this region into the pseudo-science of astrology. By reason of the ideas instilled into him by his Jewish education, Samuel attached no importance to the art of casting nativities, and only occupied himself with astronomy under its most elevated aspect. He used to boast that he was "as well acquainted with the ways of the heavens as with the streets of Nahardea." He was unable, however, to calculate the erratic movements of the comets. It is impossible to determine the extent of his astronomical acquirements, or to discover whether he was in advance of his times or simply on a par with his contemporaries. Mar-Samuel turned his knowledge of astronomy to practical account; he drew up a settled calendar of the festivals, for the purpose of delivering the Babylonian communities from continual uncertainty with regard to the exact days on which the festivals would fall, and in order to relieve them of their dependence on Palestine for the determination of the time of the appearance of the new moon. Probably out of regard for the Patriarch, and in order not to destroy the unity of Judaism, Samuel refrained from communicating his calendar to the general public, and allowed the computation of the festivals to retain its former character of a secret art (Sod ha-Ibbur). He was blamed by certain persons, however, for having in any way interfered with the calculation of the calendar. The extent of Samuel's knowledge of medicine is even less known; he boasted of being able to cure all diseases but three. An eye-salve of his invention was in great request.

Between Samuel and the founder of the Sora academy there subsisted a fraternal harmony, although the Sidra of Nahardea was eclipsed by Rab. In his modesty he willingly subordinated himself to Rab. The celebrated Shila family was possessed of the precedence in the ceremony of paying homage to the Prince of the Captivity; by them it was relinquished to Samuel, and he, in his turn, surrendered it to his comrade in Sora, contenting himself with the third place. After Rab's death Samuel was recognized as the sole religious chief of Babylon, and continued in this capacity for ten years. At first Jochanan, of Judæa, hesitated whether to acknowledge him as an authority. In the letter which the principal of the schools of Tiberias sent to Babylonia, he addressed Rab by the title of "our teacher in Babylonia," while Mar-Samuel he called simply "our comrade." The teachers of Judæa did not, in fact, give him credit for the requisite knowledge of the Halachas, basing their conclusion upon the fact that he occupied himself with other branches of science. It was in vain that Samuel sent to Judæa a festival calendar calculated for sixty years; Jochanan remarked slightingly, when the fact came to his knowledge: "At any rate he is well acquainted with arithmetic." It was not until Samuel forwarded several scrolls, filled with investigations of certain little-known diseases of animals, that he began to be respected.

It was during this period (the third century) that there occurred simultaneously in the Roman and Parthian empires certain political catastrophes which were attended with the most important results. Through their influence history acquired an altered aspect, and considerable changes were effected in the state of things existing in these two countries and their dependencies. It was impossible for Jewish history to remain unaffected by these events. During the reign of the noble Alexander Severus occurred the overthrow of the Parthian dynasty, which, beginning with Arsaces, had subsisted during four centuries. A new and more vigorous race seized the scepter, and this change of dynasty gave rise to many revolutions both at home and abroad. The author of these changes was Ardashir, or Arbachshter, as he was called in his own language, a descendant of the race of ancient Persians (Arians). Such of the Persians as still remained true to their nationality, nourished a hatred against the impure dynasty of Arsaces, on account of the semi-Grecian origin of its members, their leaning to Greek views in matters of religion, their contempt for the national faith, and finally, their impotence to check the ever-increasing conquests of the Romans. It was with them that Ardashir united himself and conspired to overthrow Artabanus, the monarch who entertained so great a reverence for Rab. A decisive battle was fought, in which Artabanus succumbed, and the neo-Persian dynasty of the Sassanides was founded by the conqueror. The race which thus obtained the upper hand is known in history by the name of the neo-Persians; the Jewish authorities called them Chebrim (Chebre), and a deteriorated residue of the stock still subsists in India under the name of the Guebres. This revolution was attended by results as important in matters of religion as in politics. In place of the indifference with which the ancient rulers had regarded the primitive worship of fire, Ardashir manifested an ardent enthusiasm for it. He proudly called himself "the worshiper of Ormuz, divine Ardashir, the King of the Kings of Iran, the offspring of a heavenly race." He ordered such of the parts of the ancient Persian law (the Zend-Avesta) as were still extant to be collected, and commanded them to be regarded as the religious code. Zoroaster's doctrine of the twin principles of light and darkness (Ahura-Mazda and Ahriman) was everywhere enforced; the Magi, the sacerdotal caste of this cult, recovered their credit, their influence, and their power, while the partisans of the Greeks were persecuted with fire and sword. The fanaticism which was thus aroused in the Magians also caused them to direct their hostile attacks against the Christians, who resided in great numbers in the districts of Nisibis and Edessa in upper Mesopotamia (conquered by the Romans), and who possessed their own schools.

The Jews were not entirely exempt from the attacks of this fanaticism, and only escaped severe persecution through their solidarity, their centralization, and their powers of defense. In the first intoxication of victory the neo-Persians deprived the Jewish courts of the criminal jurisdiction which they had been permitted to exercise until then; the Jews were admitted to no offices, and were not even allowed to retain the supervision of the canals and rivers, but they do not seem to have complained very bitterly of these measures. They were even compelled to submit to restraints upon their freedom of conscience. On certain festivals, when the Magi worshiped light in their temple as the visible representation of God (Ahura-Mazda), the Jews were not suffered to maintain any fire on their hearths, nor to retain any light in their rooms. The Persians forced their way into the houses of the Jews, extinguished every fire and collected the glowing embers in their consecrated braziers, bringing them as an offering to their temple of fire. They also dug the corpses out of the graves, because, according to their notion, dead bodies lying in the bosom of the earth desecrated this "Spenta Armaita" (holy soil). For these various reasons the majority of the teachers of the Law were not greatly prepossessed in favor of the neo-Persians. When Jochanan heard that they had triumphantly invaded Jewish Babylonia, he was greatly concerned for the fate of his Babylonian brethren, but his anxiety was allayed by the assurance that the Persians were very poor and would therefore easily allow themselves to be bought off with bribes. By reason of their semi-savage state he referred to them as "the abandoned people into whose hands the Babylonian communities had been delivered." Levi bar Sissi, who was continually traveling to and fro between Judæa and Babylon, was anxiously questioned by the Patriarch Judah II as to the character of the conquering race. With obvious prepossession in favor of the vanquished Parthians, he described them and the victorious neo-Persians in the following words: "The former are as the armies of King David, but the latter resemble the devils of hell." Little by little, however, the fanaticism of the neo-Persians moderated, and there sprang up between them and the Jews so sincere a friendship that on their account the latter relaxed the severity of the Law, and even assisted now and again at their banquets. The teachers of the Law permitted the Jews to deliver up fuel which the Magi demanded of them on the occasion of the Festival of Light, and ceased to consider this act as a furtherance of idolatry, though it would certainly have been regarded as such by the old Halacha in similar cases. Even Rab, the essence of strictness, acquiesced in the demand of the Magi, and allowed the lamps to be brought from the open street into the houses on the Sabbath on the occasion of the Festival of the Hasmonæans, in order not to give offense to the prejudices of the ruling sacerdotal class. This mutual toleration, doubtless, first made its appearance under the rule of Shabur I (242–271), the liberal-minded monarch whose friendship with Samuel has already been mentioned. This magnanimous king assured Samuel that during the many wars which he had waged against the Romans in countries thickly populated with the Jews, he had never spilt Jewish blood, except on the occasion of the capture of Cappadocia, when 12,000 Jews had been put to death as a punishment for their stubborn resistance.

The radical changes which occurred about this time in the Roman empire were also attended with important effects and reactions on Jewish history. The death of Alexander Severus was the signal for anarchy, the many-headed hydra, to rage in all its terror in Rome and the Roman provinces. During the short space of half a century (235–284) the throne was occupied by nearly twenty emperors and as many usurpers, who willingly laid down their lives to obtain the gratification of their desire to wear the purple, if only for a day, and to decree executions by the hundred. From nearly every nation which Rome had subjugated there arose an emperor who enslaved the Italian Babylon. The time of retribution had come; the birds of prey were contending for the putrefying body of the State. It was during the time of Samuel (248) that the thousandth anniversary of Rome was celebrated by the assassin-emperor Philip, an Arab by birth and a robber from his childhood; but Rome was powerful wherever its legions were stationed, except in Rome itself, the city whose senate was obliged to accept with smiling face the humiliations which it experienced at the hands of the soldier emperors, and to sanction them in servile humility by Senatus-Consulta. The Roman empire was invaded on the one hand by the Parthians, on the other by the Goths, as if in fulfilment of the sibylline threats of punishment.

Valerianus had undertaken a campaign with the intention of recovering the districts which had been conquered by Shabur. Rome now experienced the further disgrace of seeing her emperor fall into his enemy's power, and suffer all the humiliations of slavery at the hands of the haughty victor. In the eastern provinces, in the neighborhood of the mighty Persian empire, disorder and dissolution had reached a still higher degree. A rich and adventurous native of Palmyra, Odenathus by name, had collected a band of wild and rapacious Saracens around him, and he and his troops made frequent incursions from his native city into Syria and Palestine on the one side, and the region of the Euphrates on the other, plundering and laying waste the country through which they passed. Odenathus had already assumed the title of Senator. Why should he not become the emperor of the Romans, like his fellow-countryman Philip? Odenathus was known in Jewish circles as the robber captain, "Papa bar Nazar," and to him was applied the passage in Daniel's vision: "The little horn coming up among the greater horns, and having eyes like the eyes of man, and a mouth speaking great things." The predatory incursions of this adventurer were accompanied by results which were highly detrimental to the Jews of Palestine and Babylonia. He demolished the ancient city of Nahardea (259), which had formed the central point of the Jewish communities ever since the time of the Babylonian exile. It was many years before this town was able to recover itself from this destructive blow. The Amoraim of Nahardea, Samuel's disciples, were obliged to take to flight; they emigrated to the region of the Tigris. They were—Nachman, a son-in-law of the Prince of the Captivity, Sheshet, Rabba b. Abbuha, and Joseph b. Chama.

On the occasion of the destruction of Nahardea by Odenathus, Samuel's daughters, doubtless together with many others, were taken prisoners by the enemy and brought to Sepphoris. The freebooters speculated on heavy ransoms, which appeared to them more lucrative than the sale of the captives in the slave market, for it was well known that the Jews spared no expense in order to procure the release of their fellow-countrymen. Samuel's daughters had derived so much benefit from their father's profound knowledge of the Halacha that they succeeded in escaping the application of a strict law, which placed all maidens who had been taken prisoners on the same footing with those who had been dishonored, thus incapacitating them from contracting a spotless marriage. Before it was known whose daughters they were they had already recovered their freedom, and their assertion that their innocence had received no taint at the hands of the rough warriors was readily believed. When Chanina heard in Sepphoris that they were Samuel's daughters he strongly enjoined a relation of theirs, Simon b. Abba, to marry one of them.

Odenathus, the destroyer of Nahardea, gradually became a petty Asiatic prince of Palmyra or Tadmor, the oasis which King Solomon had converted into a city. The Roman empire was so feeble and tottering that it was this hitherto disregarded warrior who was obliged to oppose a bulwark to the conquests of the Persians on Roman territory. The great services which he thus rendered to the empire compelled his recognition (264) as co-emperor by Gallienus, a monarch characterized by his weakness and love of satire. Odenathus did not long enjoy this high dignity, for in 267 he fell by the hand of an assassin, instigated, as the story went, by Zenobia, his wife. After his death the regency devolved upon Zenobia, her two sons being still minors. Through her influence Palmyra, the city of the desert, was transformed into the home of imperial pomp, culture, and refined taste. A Christian report represents the empress Zenobia as a Jewess, but the Jewish authorities make no mention of this fact. No colors seem to be vivid enough for the Roman accounts of Zenobia in order to paint the picture of her strange personality. The palace of this second Semiramis, the ruins of which still bear witness to refined and artistic taste, was the meeting-place of original-minded geniuses, with whom the queen delighted to hold philosophical intercourse.

At her court resided Longinus, the refined and philosophical lover of the fine arts, who in his æsthetic work on the Sublime was unable sufficiently to express his admiration of the poetical contents of the Biblical account of the Creation, "Let there be light." Paul of Samosata, Bishop of Antioch, when accused of heresy, also found shelter at her court. Zenobia, his patroness, also seems to have had some leaning towards the fundamental truth of Judaism. The Jews were, nevertheless, not particularly well disposed towards the court of Palmyra. Jochanan, although not blind to the beauties of Greek, gave utterance to the most unfavorable opinions concerning the Palmyrene state: "Happy will he be who sees the fall of Tadmor." Subsequent generations were at a loss to explain this aversion.